Discrete
and Discreet
are NOT interchangeable! They may sound the same, they may even have the same letters, but one is not a spelling mistake of the other!
Seriously, that's the third 'well-known' book I've read recently that uses 'discrete' when what the author really meant was 'discreet'. Where can I apply to be an editor? There must be a shortage in the publishing world...
PS By the laws of the internet forum gods, there will now be multiple spelling and grammar errors inserted into my post as soon as I hit the 'submit' button. Please don't point them out to me.